As downhole instrumentation and tools have become increasingly more complex in their composition and versatile in their functionality, the need to transmit power and/or data through tubular tool string components is becoming ever more significant. Real-time logging tools located at a drill bit and/or throughout a tool string require power to operate. Providing power downhole is challenging, but if accomplished it may greatly increase the efficiency of drilling. Data collected by logging tools are is even more valuable when it is received at the surface in real time.
The goal of transmitting power or data through downhole tool string components is not new. Throughout recent decades, many attempts have been made to provide high-speed data transfer or usable power transmission through tool string components. One technology developed involves using inductive couplers to transmit an electric signal across a tool joint. U.S. Pat. No. 2,414,719 to Cloud discloses an inductive coupler positioned within a downhole pipe to transmit a signal to an adjacent pipe.
U.S. Pat. No. 4,785,247 to Meador discloses an apparatus and method for measuring formation parameters by transmitting and receiving electromagnetic signals by antennas disposed in recesses in a tubular housing member and includes an apparatus for reducing the coupling of electrical noise into the system resulting from conducting elements located adjacent the recesses and housing.
U.S. Pat. No. 4,806,928 to Veneruso describes a downhole tool adapted to be coupled in a pipe string and positioned in a well. The downhole tool is provided with one or more electrical devices cooperatively arranged to receive power from surface power sources or to transmit and/or receive control or data signals from surface equipment. Inner and outer coil assemblies arranged on ferrite cores are arranged on the downhole tool and a suspension cable for electromagnetically coupling the electrical devices to the surface equipment is provided.
U.S. Pat. No. 6,670,880 to Hall also discloses the use of inductive couplers in tool joints to transmit data or power through a tool string. The '880 patent teaches the inductive couplers lying in magnetically insulating, electrically conducting troughs. The troughs conduct magnetic flux while preventing resultant eddy currents. U.S. Pat. No. 6,670,880 is herein incorporated by reference for all that it discloses.
U.S. patent application Ser. No. 11/133,905, also to Hall, discloses a tubular component in a downhole tool string with first and second inductive couplers in a first end and third and fourth inductive couplers in a second end. A first conductive medium connects the first and third couplers and a second conductive medium connects the second and fourth couplers. The first and third couplers are independent of the second and fourth couplers. Application Ser. No. 11/133,905 is herein incorporated by reference for all that it discloses.